Structural Organization of Murine Intracisternal A Particles

Isolated murine intracisternal A particles have a distinctive set of structural properties as compared to the recognized oncogenic ribonucleic acid tumor viruses. A particles consist of two closely approximated concentric shells. The outer shell is largely, but not entirely, susceptible to treatment with detergents such as deoxycholate and Triton X-100. The inner shell is resistant to these agents and is stabilized against solubilization by sodium dodecyl sulfate as a result of disulfide bonding between its constituent proteins. The major A particle structural protein (molecular weight approximately 70,000) is contained in the inner shell. A protein component with a molecular weight of about 80,000 may be preferentially concentrated in sites of firm attachment between the inner and outer shells.     

Settlement Ecology: The Social and Spatial Organization of Kofyar Agriculture

Settlement Ecology: The Social and Spatial Organization of Kofyar Agriculture. Glenn Davis Stone. Tucson: University of Arizona Press, 1996. 256 pp.     

The vsp Locus of Mycoplasma bovis: Gene Organization and Structural Features

Major lipoprotein antigens, known as variable membrane surface lipoproteins (Vsps), on the surface of the bovine pathogen Mycoplasma bovis were shown to spontaneously undergo noncoordinate phase variation between ON and OFF expression states. The high rate of Vsp phenotypic switching was also shown to be linked with DNA rearrangements that occur at high frequency in the M. bovis chromosome (I. Lysnyansky, R. Rosengarten, and D. Yogev, J. Bacteriol. 178:5395-5401, 1996). In the present study, 13 single-copy vsp genes organized in a chromosomal cluster were identified and characterized. All vsp genes encode highly conserved N-terminal domains for membrane insertion and lipoprotein processing but divergent mature Vsp proteins. About 80% of each vsp coding region is composed of reiterated coding sequences that create a periodic polypeptide structure. Eighteen distinct repetitive domains of different lengths and amino acid sequences are distributed within the products of the various vsp genes that are subject to size variation due to spontaneous insertions or deletions of these periodic units. Some of these repeats were found to be present in only one Vsp family member, whereas other repeats recurred at variable locations in several Vsps. Each vsp gene is also 5' linked to a highly homologous upstream region composed of two internal cassettes. The findings that rearrangement events are associated with Vsp phenotypic switching and that multiple regions of high sequence similarity are present upstream of the vsp genes and within the vsp coding regions suggest that modulation of the Vsp antigenic repertoire is determined by recombination processes that occur at a high frequency within the vsp locus of M. bovis.     

Social Organization and Knowledge

This paper explores the relationship between different types of social organization, on the one hand, and different modes of knowing and types of knowledge, on the other. Some characteristic distinctions are suggested and supported with evidence, both from diverse areas of theory, and from the study of two contrasting Melanesian cultures: that of the Lavongai of New Hanover and the Tikana of New Ireland.     

Comparative Analysis of Asteraceae Chloroplast Genomes: Structural Organization,RNA Editing and Evolution

Plant Molecular Biology Reporter - Comparative chloroplast genome analysis presents new opportunities for performing molecular phylogeny studies and revealing the significant evolutionary features...     

Mummies and Mortuary Monuments: A Postprocessual Prehistory of Central Andean Social Organization

Mummies and Mortuary Monuments:. Postprocessual Prehistory of Central Andean Social Organization. William H. Isbell. University of Texas Press, 1997. 372 pp.     

The ecological basis of hunter-gatherer subsistence in African Rain Forests: The Mbuti of Eastern Zaire

The Mbuti pygmies, hunter-gatherers of the Ituri Forest of Zaire, trade forest products and labor for agricultural foods. It has been assumed that the Mbuti lived independently in the equatorial forest prior to its penetration by shifting cultivators. We assessed forest food resources (plant and animal) to determine their adequacy to support a hunting and gathering economy. For five months of the year, essentially none of the calorically important forest fruits and seeds are available. Honey is not abundant during this season of scarcity. Wild game meat is available year round, but the main animals caught have low fat content. This makes them a poor substitute for starch-dense agricultural foods, now staples in Mbuti diet. In general, in the closed evergreen forest zone, edible wild plant species are more abundant in agriculturally derived secondary forest than in primary forest. Similarly, they are more common at the savanna ecotone and in gallery forests. We suggest that it is unlikely that hunter-gatherers would have lived independently in the forest interior with its precarious resource base, when many of the food species they exploit are more abundant toward the savanna border.     

SOMITE CHONDROGENESIS : A Structural Analysis

Light and electron microscopy are used in this study to compare chondrogenesis in cultured somites with vertebral chondrogenesis These studies have also characterized some of the effects of inducer tissues (notochord and spinal cord), and different nutrient media, on chondrogenesis in cultured somites Somites from stage 17 (54–60 h) chick embryos were cultured, with or without inducer tissues, and were fed nutrient medium containing either horse serum (HS) and embryo extract (EE), or fetal calf serum (FCS) and F12X Amino acid analyses were also utilized to determine the collagen content of vertebral body cartilage in which the fibrils are homogeneously thin (ca. 150 Å) and unbanded. These analyses provide strong evidence that the thin unbanded fibrils in embryonic cartilage matrix are collagen. These thin unbanded collagen fibrils, and prominent 200–800 Å protein polysaccharide granules, constitute the structured matrix components of both developing vertebral cartilage and the cartilage formed in cultured somites Similar matrix components accumulate around the inducer tissues notochord and spinal cord. These matrix components are structurally distinct from those in embryonic fibrous tissue The synthesis of matrix by the inducer tissues is associated with the inductive interaction of these tissues with somitic mesenchyme. Due to the deleterious effects of tissue isolation and culture procedures many cells die in somitic mesenchyme during the first 24 h in culture. In spite of this cell death, chondrogenic areas are recognized after 12 h in induced cultures, and through the first 2 days in all cultures there are larger accumulations of structured matrix than are present in equivalently aged somitic mesenchyme in vivo. Surviving chondrogenic areas develop into nodules of hyaline cartilage in all induced cultures, and in most non-induced cultures fed medium containing FCS and F12X There is more cell death, less matrix accumulation, and less cartilage formed in cultures fed medium containing HS and EE. The inducer tissues, as well as nutrient medium containing FCS and F12X, facilitate cell survival, the synthesis and accumulation of cartilage matrix, and the formation of cartilage nodules in cultured somites.     

Forest Loss in Protected Areas and Intact Forest Landscapes: A Global Analysis

In spite of the high importance of forests, global forest loss has remained alarmingly high during the last decades. Forest loss at a global scale has been unveiled with increasingly finer spatial resolution, but the forest extent and loss in protected areas (PAs) and in large intact forest landscapes (IFLs) have not so far been systematically assessed. Moreover, the impact of protection on preserving the IFLs is not well understood. In this study we conducted a consistent assessment of the global forest loss in PAs and IFLs over the period 2000–2012. We used recently published global remote sensing based spatial forest cover change data, being a uniform and consistent dataset over space and time, together with global datasets on PAs’ and IFLs’ locations. Our analyses revealed that on a global scale 3% of the protected forest, 2.5% of the intact forest, and 1.5% of the protected intact forest were lost during the study period. These forest loss rates are relatively high compared to global total forest loss of 5% for the same time period. The variation in forest losses and in protection effect was large among geographical regions and countries. In some regions the loss in protected forests exceeded 5% (e.g. in Australia and Oceania, and North America) and the relative forest loss was higher inside protected areas than outside those areas (e.g. in Mongolia and parts of Africa, Central Asia, and Europe). At the same time, protection was found to prevent forest loss in several countries (e.g. in South America and Southeast Asia). Globally, high area-weighted forest loss rates of protected and intact forests were associated with high gross domestic product and in the case of protected forests also with high proportions of agricultural land. Our findings reinforce the need for improved understanding of the reasons for the high forest losses in PAs and IFLs and strategies to prevent further losses.